Immediate ban on new cesspools in Puna?

[MarkP]

My understanding is that it's all about giving the bacteria that treat the wastewater a place to live that meets their needs (lots of surface area in an aerobic environment) and arranging for the wastewater to trickle slowly past so the bacteria can do their job. The solids are just organic matter and aren't really any worse than the liquid wastewater but they would clog the rest of the system unless dealt with. The septic tank neatly does a couple of jobs. It captures solids so they don't clog the leach field, and it slows down the pulses of wastewater so the leach field sees more of a steady trickle, which allows the bacteria to work on the wastewater better.

Because of the porosity of the soil here cesspools can last indefinitely without maintenance. Solid waste eventually breaks down to almost nothing. Compared to a properly designed septic system though there is almost no opportunity for the wastewater to be treated aerobically before descending towards the water table. Leach fields are only a couple of feet below grade and are designed to be aerobic with tons of surface area and the wastewater trickles slowly past in a carefully metered fashion. Cesspools are at least 10 feet deep to start with and if they happen to intersect with a big crack the wastewater could be hundreds of feet down in minutes. They function as more of an injection well than a treatment system.